Casting may be used to form articles that are used “as cast,” but generally cast parts are subject to further material processing operations such as machining, forging, rolling, or extruding. Many casting operations result in undesirable amounts of porosity and shrinkage. Often these problems are not identified until either the “as cast” article fails or subsequent material processing operations uncover the problem with the cast part. What are needed therefore are improved methods for reliably casting materials.